Ryan to Mars: An Unexpected Journey: May 27, 2013

Show Notes: May 27th, 2013 UTC

Back from a much needed rest, the York Universe team was full of energy! With so much to discuss (two week break and all…) and only an hour to chat, it turned into a very packed night! Among other news, the York Universe team attended the “What’s Up in Space?” event hosted by the Astronuts Kids Space Club to present to engage children with astronomy activities. Ryan pre-recorded an episode of Curiosity Corner…and then introduced it himself, showing that it is possible to be in two places at once. Finally, we discussed both Exoplanets and Giant Elliptical galaxies. Thanks for listening all! Podcast and show notes below.

This week in space/astronomy history:

1. May 26 1973: Skylab, USA Space Station, launched. Skylab, which was America’s first space station, was manned for 171 days by three crews during 1973 and 1974. The space station included the Apollo Telescope Mount (ATM), which astronauts used to take more than 150,000 images of the Sun. Skylab was abandoned in February 1974 and re-entered the Earth’s atmosphere in 1979.

4. May 31 2008: Kibo Laboratory is added to the ISS, the largest module in orbit. Launched with the STS124 mission.

News:

1. Ring Nebula gets a facelift. The Hubble Space Telescope was used to create the most detailed view of the Ring Nebula to date. The resulting image has allowed astronomers to create a 3D representation of the object. Science Daily has a great article on the new image here.

2. 2nd Annual What’s Up in Space? hosted by the Astronuts Kids Space Club
Each year, The club organizes a fun afternoon of astronomy and space science presenters covering topics from rocketry to what constellations look like. The York Universe team was represented by Jesse, Lianne, and Ryan with the addition of Julie Tome (York Observatory Alumni). Together they created a 3D representation of the Orion Constellation using this paper written by Dr. Daniel Brown. Stay tuned to the York Universe website for pics of the event.

3. The European Southern Observatory’s Very Large Telescope (VLT) celebrates 15 years of successful observations. That was this week in history, May 25, 1998.

4. Conjunction of Mercury, Venus, Jupiter in north west sky.

5. Kepler Space Telescope in Safe Mode – Michael sobbing lol

6. Curiosity Corner (Pre-Recorded) with Ryan Marciniak

Major Topics Discussed:

Rocky planets have now been discovered using the transit method through surveys such as Kepler. This method of detection allows for the identification by the fraction of light that is diminished when the planet passes in front of it’s host star. The amount of light that is blocked is proportional to the ratio between the radius of the planet and the radius of the star. The density of the planet can be calculated using radius and the mass of the planet (through the radial velocity method).

Recently, we have identified a few planets which may have rocky surfaces! But, due to the uncertainties in the planets’ radii and masses, the composition of some planets is still unknown.
Earlier this year Hu et. al released a paper whose purpose was to identify terrestrial exoplanets through the identification of “mineral-specific” spectral features. Using the well-observed analogues of airless exoplanets (the Moon, Mars, Mercury) they were able to place significant spectroscopic constraints on the surface composition of rocky planets in the solar system.

They proposed using a new method of identifying rocky exoplanets through infrared spectroscopy in order to identify the mineral composition of the surface of exoplanets. The light (both reflected stellar radiation and planetary thermal emission) from the exoplanet can be observed through direct imaging, and through secondary eclipses (if the planet is transiting). A secondary eclipse is when the planet is blocked by it’s star. It allows for the direct measurement of the planet’s light as the light before and after this eclipse are compared revealing the light from the planet.

As the resolution of the spectra from exoplanets is very low it is essential to focus of the most prominent spectral features from an exoplanet. They developed a framework to calculate the spectra of a planet (integrated over the entire observable disk). So far studies have used the reflected light from vegetation and liquid water oceans. This paper is implementing an approach to investigate the spectral features of solid materials on the surface.

They focused on airless, rocky exoplanets with solid surfaces. They ensured that the planetary thermal emission and reflected stellar emission be at separate wavelengths by requiring the temperature to be below the melting temperature for common minerals. In the end they found that rocky silicate surfaces lead to unique features in the planetary emission. They also found that surface water ice has a unique absorption feature in the reflected stellar light. Planetary surfaces of different compositions can have very different overall reflectivity. But, the characterization of airless rocky exoplanets’ solid surfaces is not inherently more difficult than the characterization of their atmospheres.

If suitable targets are found by thermal emission it is possible to observe rocky surfaces with current equipment! This will be best observed for planets close to the host star (though not too close so as to not melt the surface) especially for smaller and cooler M dwarfs. JWST will likely be able to detect silicate surfaces around sun-like stars.

2. How you make a massive Elliptical
It appears that the massive Elliptical galaxies that are known today were probably formed approximately 10 billion years ago (approximately a redshift of z=2), and during formation they likely had star formation rates at 100s of solar masses per year. To compare, the Milky Way is currently forming new stars at a rate of 1 solar mass per year. Elliptical galaxies are both very old, and very gas depleted. A high star formation rate is needed to turn all the gas from galaxy mergers into stars to make the Ellipticals gas depleted. In order to prove this theory, astronomers need to go out into the Universe and find progenitor objects that have high star formation rates. These have been found and are called sub-millimeter-bright (SMB) galaxies. However, there has always been a missing link in the chain. While the SMB galaxies can explain the formation of typical Ellipticals (average mass), astronomers had yet to find a SMB that can explain the especially massive Elliptical galaxies. If no SMB had been observed with a high enough star formation rate to explain these Ellipticals, then perhaps another process should be invoked to deplete all the gas of the galaxies (such as black hole feedback).

A large team from a multitude of institutions has discovered a merger of two massive SMB galaxies at redshift z=2.3 (10.8 billion light years away), which exhibits a star formation rate of 2000 solar masses per year, enough to explain the massive Ellipticals we see today. This is the brightest, most luminous, and most gas rich merger of two sub-millimeter-bright galaxies known. Of note is the merger, named HXMM01, has been magnified approximately 2x by way of gravitational lensing.

Massive galaxies with as much gas as this merger are not created in cosmological simulations. However, at such high star formation rates, HXMM01 will go from 50% gas fraction to 20% gas fraction in just 70 Myr, which will bring it down to what simulations DO create.

HXMM01 is illustrating the rapid formation of an extremely massive giant Elliptical galaxy. It will have a final mass of approximately 4×10^11 solar masses, comparable to the massive Ellipticals at z~2. It’s stellar population will appear ‘quenched’ by approximately z=1.7. Typically, gas poor mergers have been invoked to explain how Elliptical galaxies can get so large yet have no star formation. However, this object shows that an massive Elliptical can be created directly from a gas-rich situation.